Python: Store rotation / normal in bezier curve point?
Bezier curve objects can store a property called tilt.
It is basically a per point rotation value or normal that controls it's twisting on a per.vertex basis.

It can be set through the UI in edit mode under the Properties Shelf > Transform > Tilt or through the Python API with bpy.types.BezierSplinePoint.tilt



As far asI know curves don't support arbitrary data layers per vertex like BMesh does, but I may be wrong.